As IrishSights said different EU countries have different regulations. Poland has one of the most liberal drone's regulations. However, to perform commercial operations UAVO diploma is required. To get it you must pass an exam consisting of a theoretical part (air law, a man as the operator, the construction of MR, safety) and practical (in ATII mode).

The problem is that locally the legislation is 20 years old, is in regards to regular airplanes/helicopters and they basically made an additional guideline that is vague and basically makes commercial flight permission cost the same as if you were flying a sightseeing Cesna, which is ridiculous.
I would much rather get a permit in an EU country that has clear guidelines and permits flight in the whole EU, since the base legislation should be the same. Although I don't know if its possible for a non-resident and if any country offers something like that.